1. Field of the Invention
The present invention generally relates to a fuel injection control system and, in particular, to a fuel injection control system having a throttle device in which a throttle valve is driven by an actuator.
2. Description of Related Art
There is known a fuel injection control system for an internal combustion engine in which acceleration and deceleration conditions of a vehicle are detected by various sensors in order to perform fuel injection according to a travel condition of the vehicle. However, over-shoots or under-shoots may be produced in outputs of such sensors due to various factors, so that it is difficult to make a judgment on the acceleration and deceleration conditions of the vehicle.
Japanese Patent No. 2849322 discloses a fuel injection control system adapted to judge acceleration and deceleration conditions of a vehicle based upon an output of a pressure sensor provided in an intake pipe of an internal combustion engine. The JP '322 system is adapted to change basic values to judge the acceleration and deceleration conditions at the end of accelerating and decelerating. The JP '322 arrangement is intended to prevent a judgment of the deceleration condition due to an over-shoot of a pressure sensor value when accelerating by quickly open-operating a throttle device to a fixed opening. Similarly, the JP '322 arrangement prevents a judgment of the acceleration condition due to an under-shoot of the pressure sensor value when decelerating by quickly bringing the throttle device to a fully closed condition.
In a TBW (throttle-by-wire) system that drives a throttle valve by an actuator such as an electric motor, etc., according to operation of a throttle device (throttle grip, throttle pedal, etc.) by an operator, there is a possibility that a real throttle valve opening (hereinafter referred to as a real TH valve opening) will over-shoot and under-shoot relative to a target opening of the throttle valve (hereinafter referred to as a target TH valve opening) due to mechanical characteristics such as gears, springs, etc. which are contained in the actuator and the throttle device.
Concretely, there is a possibility that, at the time of acceleration-operating, such as quickly open-operating of the throttle device and maintaining the opening of the throttle valve, the real TH valve opening once over-shoots relative to the target TH valve opening and then under-shoots. At this time, in a system that judges the acceleration and deceleration conditions of a vehicle according to the real TH valve opening and controls a fuel injection quantity, there is a possibility that, though the throttle device is maintained at a fixed opening, it is judged that the vehicle is in the accelerated or decelerated condition, and the fuel injection quantity is decreased and increased. As such, the engine operation and riding experience may not match the desires of the operator, as evidenced by the condition of the throttle device.
In the related art disclosed in the aforementioned JP '322 patent, over-shoot and under-shoot of the real TH valve opening relative to the target TH valve opening due to mechanical characteristics is not taken into consideration. Therefore, there may result conditions, as mentioned hereinbefore, in which the engine operation and riding experience do not correspond to the throttle setting input by the user via the throttle device.